FSA201 datasheet(4/21 Pages) ONSEMI

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FSA201 Rev. 1.2.2

Functional Description

The FSA201 is a combined USB and audio switch that

enables sharing the D+/D- lines of a USB connector with

stereo audio CODEC outputs. The switch is optimized

for full-speed USB signals and includes an automatic

VBUS-detection circuit. When a USB connector, rather

than a headphone, is connected to the ultra-portable

device the switch is automatically configured for full-

speed USB data transfer. If no VBUS is detected, and yet

VAUDIO is present, the switch is configured for the low-

distortion audio switch path. The audio switch path also

handles

negative

signals

(down

-2V),

which

eliminates the need for large coupling capacitors.

For those applications where the VBUS is generated as a

self-powered device or where VBUS is not removed, the

ASEL pin provides the ability to switch, under software

control, to the audio path. The ASEL pin is internally

terminated by a resistor to GND (typical value 3M

) and

requires no connection for the standard ultra-portable

(cell-phone, MP3, or Portable Media Player). In an

application where the supply to the FSA201 VBUS pin is

not guaranteed to be removed, a GPIO pin can be used

to switch out of full-speed USB mode into audio mode,

using the ASEL pin.

The FSA201 VBUS pin must be connected directly to

VBUS or a supply > 3.8V, not an LDO regulated down to

3.6V or a Vbat-generated supply that may fall below 3.8V

in normal operation (see the Application Diagram).

Application Diagram

bus

audio

Switch Select

Control Circuitry

D+/R

D-/L

D+

D-

Sel

Rpd

GND

Audio

CODEC

FS-USB

Source

3.0V - 3.6V

USB

Mini -AB

Connector

bus

Figure 4.

Application Diagram

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